We are probably used to amplifiers being used to, amplify, the signal coming from something like an electric guitar or a microphone. However, they are also very important in the world of synthesizers.
In the classic design of a synthesizer, the signal is always running, kind of like a dial tone on a landline. It’s basically sitting in something called the Operational Amplifier (or Op-Amp). We can set up a synth in a way so that when we press a note on our keyboard, it turns on the amp and let’s sound through. When we stop pressing the keyboard, the amp is turned off.
This constant flicking of a switch is known as the gate, and it’s one of the first things that you do when designing a synth, both analog and virtual.
In Pure Data and Max, the amp object is represented by the *~, which is also known as the multiplier.